Imaging of Blunt and Penetrating Abdominal Trauma

Abstract

Trauma is the leading cause of morbidity and mortality among people younger than 45 years of age. Traumatic injury to the abdominal organs, with ensuing exsanguination, is the primary cause of death. Of all abdominal traumatic injuries presenting to hospitals, blunt trauma comprises approximately 90% and typically results from a motor vehicle collision or a fall. Penetrating trauma accounts for the remaining 10% and is often a result of a bullet or knife injury. The evaluation of blunt or penetrating abdominal trauma can be one of the most challenging and resource-exhaustive aspects of acute trauma care.

Introduction

Trauma is the leading cause of morbidity and mortality among people younger than 45 years of age. Traumatic injury to the abdominal organs, with ensuing exsanguination, is the primary cause of death [1]. Of all abdominal traumatic injuries presenting to hospitals, blunt trauma comprises approximately 90% and typically results from a motor vehicle collision or a fall. Penetrating trauma accounts for the remaining 10% and is often a result of a bullet or knife injury. The evaluation of blunt or penetrating abdominal trauma can be one of the most challenging and resource-exhaustive aspects of acute trauma care.

In 1988, the American Association for the Surgery of Trauma (AAST) devised a set of organ injury scales (OISs) based on findings at surgical exploration. The OISs have now been defined by computed tomography (CT) criteria [2]. Accurate noninvasive assessment of injuries with CT is beneficial and can guide management. Since the development and application of these CT-based criteria, nonoperative management for blunt abdominal trauma has become increasingly common, particularly in hemodynamically stable patients. The accumulated evidence has demonstrated that minimally invasive management of blunt abdominal trauma, instead of laparotomy, results in improved survival rates. Analogously, managing penetrating abdominal trauma with laparotomy results in a negative or nontherapeutic procedure in 15–25% of cases, prompting a movement toward more conservative management algorithms [3].

Currently, multidetector computed tomography (MDCT ) with intravenous contrast is the “gold standard” diagnostic imaging examination in hemodynamically stable patients who have intra-abdominal fluid by focused assessment with sonography for trauma (FAST ) [4]. Many studies have reported that MDCT has high sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in injuries to the liver, spleen, kidney and urinary bladder, hollow viscus, and major vascular structures [2,3,4,5].

FAST

FAST is a useful diagnostic tool when performed in the acute setting because it can demonstrate intra-abdominal fluid, a finding that suggests significant organ injury, with a sensitivity of 90–93% [4]. FAST is often performed after the secondary assessment or during resuscitation efforts. Identification of intra-abdominal free fluid on FAST (Fig. 9.1) in a hemodynamically unstable patient is regarded as synonymous with hemoperitoneum, thereby directing the surgeon to consider the abdomen as the major source of blood loss and prompting emergent laparotomy instead of CT. Conversely, a positive FAST in a hemodynamically stable patient should be followed by a CT scan to determine the source of the fluid. Table 9.1 summarizes the etiologies of positive FAST.

Fig. 9.1

FAST. Ultrasound image from a FAST exam show small amount of fluid adjacent to the spleen (arrow)

Table 9.1 Etiologies of positive FAST

Shortcomings of FAST include its inability to qualitatively grade the extent of organ injury and its low (34–55%) sensitivity for direct demonstration of blunt abdominal injury [4]. Other limiting factors include inability to demonstrate small amounts of free fluid, operator dependence, limited accuracy in the retroperitoneum, and large body habitus.

Liver

The liver is the most frequently injured solid abdominal organ in blunt and penetrating trauma. Hepatic injury in patients who have sustained blunt trauma has been reported to occur in 1–8% and in penetrating trauma in up to 39% [1, 6]. However, with utilization of abdominal CT in the severely injured patient, hepatic injuries can be detected in up to 25% of those with blunt trauma [7]. CT also helps in detection of associated injuries including spleen (21%) and kidney (9%) and bowel (4%). Mortality rates from blunt or penetrating liver injury have been reported to range from 2.8 to 11.7% [6, 8].

Nonsurgical management is the preferred strategy for hemodynamically stable patients with blunt liver injury. Accurate characterization of the extent of the injury by CT assists the managing provider with specific information that can be followed and categorized by the AAST OIS criteria (Table 9.2).

Table 9.2 AAST organ injury scale for liver

Hepatic injuries detected by CT can be classified as lacerations, hematomas, active hemorrhage, and juxtahepatic venous injuries. Hepatic laceration is the most common type of parenchymal liver injury; it appears as an irregular, linear, or branching low-attenuation region on contrast-enhanced CT (CECT) (Fig. 9.2). Lacerations are further divided into superficial (<3 cm) or deep (>3 cm).

Fig. 9.2

Hepatic laceration from gunshot wound. (a and b) Contrast-enhanced CT demonstrates a deep hepatic (straight arrow) as well a right renal laceration (curved arrow). There is a bullet fragment (white arrowhead) located in the right posterior abdominal wall. (c) Contrast-enhanced CT demonstrates a metallic density bullet fragment located centrally with in the right lobe of liver. The liver laceration is obscured by the extensive beam-hardening artifact produced by the bullet fragment

Hematomas that present in blunt liver trauma are designated as subscapular or intraparenchymal. On CECT, a subcapsular hematoma appears as an elliptical collection of low-attenuation blood between the capsule of the liver and the enhancing liver parenchyma (Fig. 9.3). Intraparenchymal hematomas are characterized by focal low-attenuation regions with poorly defined, irregular margins in the liver parenchyma on CECT (see Fig. 9.2). Active hemorrhage is diagnosed by identification of a focal high-attenuation area representing a collection of extravasated contrast. Active vascular extravasation can often be differentiated from clotted blood by measuring the CT attenuation coefficient. The attenuation of clotted blood ranges from 28 to 82 Hounsfield units (HU) (mean, 54 HU) (Fig. 9.4a), whereas active arterial extravasation ranges from 91 to 274 HU (mean, 155 HU) (see Fig. 9.4b) [10]. Active contrast extravasation (ACE ) changes its appearance over time; such a pattern can be demonstrated with multiphase vascular imaging, that is, during the arterial, portal venous, or delayed phases. On later vascular phase imaging, a region of ACE will increase in size and often pool or mix with noncontrasted blood in the adjacent hematoma. Table 9.3 summarizes the CT findings of hepatic injuries.

Fig. 9.3

Hepatic lacerations . (a and b) Contrast-enhanced CT in two different patients show a deep (>3 cm) hepatic laceration (grade III and grade IV liver injury) (curved arrows) due to stab and gunshot injury, respectively. (c) Contrast-enhanced CT shows a wedge-shaped liver laceration due to stab injury and enhancing pseudoaneurysm (arrowhead). (d) Contrast-enhanced CT shows a large perihepatic hematoma and active extravasation (arrowhead) arising from a gunshot injury related superficial liver laceration (curved arrow). (e) Contrast-enhanced CT shows grade IV liver injury with devascularization of >25% of the right lobe of the liver (arrowhead)

Fig. 9.4

Clotted blood versus contrast extravasation. (a) Contrast-enhanced CT image shows clotted blood (arrow) adjacent to the spleen. (b) Contrast-enhanced CT image shows small amount of active contrast extravasation (arrow) adjacent to the spleen

Table 9.3 CT findings of hepatic injuries

Hepatic lacerations or hematomas that extend into a major venous structure indicate a severe injury and have been reported to require surgical management approximately 6.5 times more frequently than injuries not involving the hepatic veins or inferior vena cava (IVC) [11]. A CT finding that may indicate liver injury is periportal low attenuation paralleling the portal vein and its branches. Periportal low attenuation adjacent to a hepatic laceration may represent extension of hemorrhage into the periportal connective tissue, although this finding is nonspecific. It can also represent distention of the periportal lymphatic vessels as can be seen after aggressive fluid resuscitation, tension pneumothorax, or pericardial tamponade [12].

Spleen

Currently, 60–80% of patients who sustain blunt splenic injury are managed nonoperatively with a success rate near 95% [2]. Nonoperative management of isolated splenic injury is contingent on hemodynamic stability. Inevitably, failure of nonoperative management correlates with the presence of ACE on CT scan as well as with the radiological grade of the injury per the AAST criteria [9] (Table 9.4).

Table 9.4 AAST organ injury scale for spleen

CECT can accurately diagnose the four common types of splenic injury: hematoma, laceration, active hemorrhage, and vascular injuries [13]. Splenic hematomas may be classified as subcapsular or intraparenchymal. On CECT, a subcapsular hematoma appears as an elliptical, low-attenuating collection between the splenic capsule and the enhancing splenic parenchyma (Fig. 9.5). Acute lacerations have a jagged or sharp margin and appear on CECT as a linear or branching low-attenuation area.

Fig. 9.5

Shattered spleen (Grade 5 injury). Contrast-enhanced CT shows shattered spleen (arrow) with perisplenic hematoma

Active hemorrhage in the spleen is represented as an irregular or linear focus of contrast extravasation on CECT. Active hemorrhage may be seen in several locations: within splenic parenchyma or subcapsular space or intraperitoneally. Differentiating between ACE (range 85–350 HU, mean 132 HU) and hematoma or clotted blood (range 40–70 HU, mean 51 HU) is accomplished by measuring the attenuation coefficient [13].

Splenic vascular injuries include posttraumatic pseudoaneurysms and arteriovenous (AV) fistulas. A splenic pseudoaneurysm will appear as a well-circumscribed focus of increased attenuation in comparison to the enhancing splenic parenchyma (Fig. 9.6). An AV fistula is best demonstrated by early splenic vein enhancement. Both of these vascular injuries are best seen on arterial phase imaging and can be difficult to detect on portal venous phase or delayed (renal excretory phase) imaging. If a splenic pseudoaneurysm is suspected on early arterial phase imaging, it is helpful to distinguish this finding from ACE by noting the characteristics on delayed imaging. Specifically, on delayed imaging, a pseudoaneurysm will remain the same size and demonstrate similar density to the aorta, but ACE will increase in size and remain with high density. Splenic vascular lesions can be managed successfully by splenic arteriographic embolization, which improves the success rate of nonoperative management of blunt splenic injuries from 87 to 94% [14, 15]. Table 9.5 summarizes CT findings of common types of splenic injury.

Fig. 9.6

Splenic pseudoaneurysm . (a) Contrast-enhanced CT demonstrates a pseudoaneurysm (arrowhead) within the splenic parenchymal laceration. (b) Conventional splenic artery angiogram demonstrates the splenic arterial branch pseudoaneurysm (arrowhead)

Table 9.5 CT findings of common types of splenic injury

Pancreas

Pancreatic injuries have been reported as high as 12% in victims of blunt trauma and 6% in those with penetrating trauma. Typically, pancreatic injuries are associated with other intra-abdominal injuries 50–98% of the time [13]. The clinical diagnosis of pancreatic injury may be difficult, particularly when isolated. Owing to the retroperitoneal location of the pancreas, peritonitis from a pancreatic injury may take hours to days to manifest. In addition, serum and urinary amylase levels are unreliable markers for the diagnosis of pancreatic injury [16].

CECT is the modality of choice for diagnosing pancreatic injury; its reported sensitivity and specificity is as high as 85% [17]. CECT findings of pancreatic injury may be subtle, and the pancreas may appear normal immediately post-injury. Of primary importance is evaluation of the pancreatic duct because its integrity or lack of integrity directs management.

A pancreatic injury can be categorized as contusion, laceration, or transection. A pancreatic contusion may appear as diffuse enlargement of the pancreas or as focal low attenuation or heterogeneity. Pancreatic lacerations are demonstrated by linear, irregular low-attenuation areas within the normally enhancing parenchyma (Fig. 9.7). A pancreatic transection may be difficult to diagnose with CT unless there is low-attenuation fluid collection separating the two edges of the transected pancreas. Table 9.6 summarizes CT findings of common types of pancreatic injury.

Fig. 9.7

Pancreatic injury . (a and b) Contrast-enhanced CT in two patients demonstrates pancreatic laceration (arrow) with disruption of the main pancreatic duct. (c) Endoscopic retrograde cholangiopancreatography image showing pancreatic duct discontinuity (curved arrow) and extravasation of contrast from the ductal disruption (arrowheads)

Table 9.6 CT findings of common types of pancreatic injury

The position of the pancreatic laceration in relation to the superior mesenteric artery as well as the depth of the laceration helps predict pancreatic ductal disruption, which occurs in up to 15% of pancreatic trauma [13, 17]. The superior mesenteric vessels provide a landmark for dividing the pancreas into proximal and distal portions with injury to the proximal pancreas usually associated with more severe injury. A laceration of the pancreas involving >50% of the anteroposterior diameter of the pancreatic body or tail is often associated with ductal disruption.

There are several nonspecific CT findings associated with pancreatic trauma, the most common of which is thickening or infiltration of the anterior pararenal fascia. Additional nonspecific CT findings include blood/fluid tracking along the mesenteric vessels, fluid in the lesser sac, fluid between the pancreas and splenic vein, or infiltration of the peripancreatic fat with fluid or hemorrhage [13].

Kidney

The kidney is the most commonly injured urogenital organ in trauma. Approximately 10% of all significant blunt abdominal traumatic injuries include a renal injury, and of those, 80–90% are managed nonoperatively. The goal of conservative management is to preserve organ integrity and reduce the complication rate. Historical evidence shows that hemodynamically stable patients with kidney injuries who undergo surgical exploration have a much higher incidence of nephrectomy [4]. Blunt trauma accounts for approximately 90% of renal trauma, while penetrating trauma accounts for approximately 10%. Nonsurgical management is more commonly advocated in blunt renal injuries, but conservative protocols have also been applied to penetrating renal injuries [18, 19]. However, penetrating trauma is more frequently associated with major renal injury and frequently requires invasive treatment, as it is more often associated with hemodynamic instability and damage to surrounding abdominal organs [20]. Indications for renal imaging include gross hematuria and penetrating or blunt trauma with hematuria. The imaging modality of choice to evaluate the kidneys after trauma is CECT.

Renal injuries may be classified as lacerations, contusions, or renovascular injuries, which determine the radiological grade of the injury per AAST criteria (Table 9.7). Renal contusions are visualized as poorly marginated, round or ovoid areas of low-attenuation and show a delayed or persistent nephrogram when compared to normal adjacent renal parenchyma. Hematomas can be categorized as subcapsular or perinephric. On an unenhanced CT, a subcapsular hematoma (Fig. 9.8) is seen as an eccentric hyperattenuating fluid collection confined between the renal parenchyma and renal capsule. However, on a CECT a subcapsular hematoma will be hypoattenuating compared to the normal enhancing renal parenchyma. A subcapsular hematoma may also exert a mass effect on the renal contour and can cause decreased perfusion in extreme cases. A perinephric hematoma is a poorly marginated, hyperattenuating fluid collection (45–90 HU) that is confined between the renal parenchyma and the Gerota’s fascia [21]. Other findings associated with a perinephric hematoma are thickening of the lateroconal fascia, compression of the colon, and displacement of the kidney.

Table 9.7 AAST organ injury scale for kidney

Fig. 9.8

Page kidney . (a and b) Axial and coronal contrast-enhanced CT images demonstrate subcapsular hematoma (arrowhead) compressing the left renal cortex

Renal lacerations are visualized as hypoattenuating, irregular wedge-shaped, or linear parenchymal defects or clefts (Figs. 9.9 and 9.10). The most severe form of renal laceration, termed a “shattered kidney,” represents a kidney that is fractured into multiple fragments. It is often associated with devitalized renal tissue, injuries to the collecting system, severe hemorrhage, active arterial bleeding, and compromise in the excretion of contrast material [21]. Table 9.8 summarizes CT findings of common types of renal injury.

Fig. 9.9

Renal laceration . (a) Axial contrast-enhanced CT demonstrating a grade II laceration (arrowhead) with small perinephric hematoma. (b) Axial contrast-enhanced CT demonstrates grade V shattered kidney (arrowhead) and extravasation of urine (white arrow) into the perinephric space

Fig. 9.10

Renal injury, CECT. (a and b) Axial and sagittal contrast-enhanced CT demonstrate right renal laceration with extravasation of contrast (arrowheads) into a perinephric hematoma

Table 9.8 CT findings of common types of renal injury

The depth of a renal laceration is important as it relates to the renal collecting system. If a laceration extends into the collecting system, this is consistent with a higher-grade injury (IV or V instead of III). Renal pelvis or collecting system involvement can be demonstrated by urine extravasation, which is seen as a perinephric low-density fluid collection on arterial or portal venous phase imaging. Suspected urine extravasation can be differentiated from hematoma by the presence of contrast extravasation, which is only seen on the delayed renal excretory phase images.

Urinary Bladder

Bladder injuries are caused by blunt or penetrating trauma. Blunt trauma accounts for 60–85% of bladder injuries, whereas penetrating trauma accounts for 15–40% [22]. The conventional mechanism of injury to the bladder in blunt abdominal trauma is rapid increase of the intravesical pressure resulting in a tear along the intraperitoneal portion of the bladder wall. Bladder injury is more common among those sustaining a seatbelt or steering wheel injury.

Bladder rupture should be suspected when a patient presents with gross hematuria, pelvic fluid, and/or pelvic fractures. Certain types of pelvic fractures are associated with bladder rupture; these include sacral, iliac, and pubic rami fractures as well as pubic symphysis diastasis and sacroiliac joint diastasis [23]. In patients with pelvic fractures, bladder injury occurs in approximately 10%; however, traumatic extraperitoneal ruptures of the bladder are predominantly associated with pelvic fractures [24]. CT cystography or conventional fluoroscopic cystography should be performed following CT of the abdomen and pelvis in hemodynamically stable trauma patients with:

• 1. Gross hematuria, or

• 2. Pelvic fracture (other than an isolated acetabular fracture) plus microhematuria (>25 RBC/HPC), or

• 3. Microhematuria and pelvic fluid.

CT cystography has a similar sensitivity and specificity to conventional fluoroscopic cystography and provides a more complete and more sensitive evaluation of the urinary bladder than a conventional abdominal and pelvic CT [25].

On abdominal CT, findings suggestive of urinary bladder injury or rupture include the presence of free fluid in the pelvis with no obvious source, urinary contrast extravasation, bladder wall discontinuity, and the presence of any foreign body within the bladder wall (Figs. 9.11, 9.12, and 9.13). On CT cystography, extraperitoneal injuries can be distinguished from intraperitoneal injuries by the location of the extravasation in relation to the peritoneal reflection. An extraperitoneal injury is below the peritoneal reflection and will demonstrate contrast extravasation in the classic “flame-shaped” or “molar tooth” configuration as the contrast penetrates into the paravesical tissues. In the case of intraperitoneal bladder injuries, the perforation is above the peritoneal reflection and extravasated contrast will outline bowel loops. Injuries to the neck of the bladder will show extravasation near the base of the bladder. The pattern of contrast extravasation on cystography is of foremost importance and will guide management of the patient. Table 9.9 summarizes CT findings of urinary bladder injury.

Fig. 9.11

Intraperitoneal bladder rupture. (a and b) Coronal CT cystogram image demonstrating large amount of intraperitoneal contrast (arrows) leaking from the dome of the urinary bladder (arrowhead) and outlining the small bowel loops

Fig. 9.12

Intraperitoneal rupture of the urinary bladder. Sagittal CT cystogram image demonstrating intraperitoneal contrast (arrow) outlining the pelvis and bowel loops

Fig. 9.13

Urinary bladder rupture . (a) Ultrasound image of the pelvis demonstrating direct transperitoneal communication (arrow) between urinary bladder and a large pelvic urinoma. (b) Cystogram study depicts extravasation of contrast from the urinary bladder into the extraperitoneal space (arrow). (c) CT cystogram demonstrating Foley catheter bulb (arrow) located outside the urinary bladder in a large pelvic hemorrhagic fluid collection

Table 9.9 CT findings of urinary bladder injury

Urethra

Injuries to the urethra are most often caused by a displaced anterior arch pelvic fracture or iatrogenic manipulation [26]. Approximately 10–25% of patients with a pelvic fracture also have urethral trauma. Urethral injury is most often diagnosed with a retrograde urethrogram (RUG), which should be performed prior to insertion of a urethral catheter to avoid further injury. The ultimate goal of an RUG following trauma is to evaluate the integrity of the urethra and to determine if the urethra is “watertight.” Contrast leakage from the urethral lumen during an RUG is diagnostic for urethral injury (Fig. 9.14). An RUG can also demonstrate strictures, which can be long-term sequelae of urethral injury.

Fig. 9.14

Urethral injuries by RUG. (a) RUG demonstrating leakage of contrast (arrow) from the bulbous urethra. (b) RUG demonstrating urethral narrowing (arrowhead) due to extrinsic compression from a penile shaft hematoma. There is no disruption of the urethra in this patient

Urethral injuries are divided into two categories based on the anatomical site of the injury. Posterior urethral injuries are located in the membranous and prostatic urethra. Anterior urethral injuries are located distal to the membranous urethra. Typically, both posterior and anterior urethral injuries are the result of blunt trauma. Penetrating trauma, which includes gunshot and stab wounds, most often affects the penile urethra (Fig. 9.15).

Fig. 9.15

Urethral injury from shotgun pellets. Contrast-enhanced CT demonstrates multiple metallic foreign bodies (arrowheads) in the corpora cavernosa and spongiosum of the penis

Radiologists employ two different classification systems for grading urethral injuries. The Goldman’s classification (Table 9.10) is most commonly used by urologists and includes urethral injuries as well as bladder injuries that simulate posterior urethral injury. The second classification system is the AAST Organ Injury Scale for urethral injuries (Table 9.11). Imaging of the urethra with an RUG is the reference standard for urethral injury; however, with the widespread use of CT, it is vital to be familiar with CT findings indicative of urethral injury. These findings include indistinct urogenital diaphragmatic fat plane, indistinct prostatic contour, hematoma of the ischiocavernosus and obturator internus muscles, and obscuration of the bulbocavernosus muscle [27,28,29].

Table 9.10 Goldman’s classification for urethral injuries

Table 9.11 AAST organ injury scale for urethra

Bowel and Mesentery

Unidentified bowel and mesenteric injuries carry significant morbidity and mortality secondary to complications arising from peritonitis. Injuries to the bowel and mesentery occur in approximately 5% of patients sustaining blunt abdominal trauma and 30% in patients sustaining penetrating trauma to the abdomen [2, 6, 13]. Similar to pancreatic injury, the initial physical examination on a patient with mesenteric injury may be misleadingly normal. Classic peritoneal signs may be present in only one-third of patients [30].

Injury to the bowel and mesentery is most often diagnosed with CECT. However, there is no single CT sign that is considered both sensitive and specific for bowel or mesenteric injury. CT findings suggestive of a mesenteric injury include contrast extravasation into the mesentery, vascular beading/abrupt termination, focal mesenteric hematoma or infiltration, bowel wall thickening, or abnormal enhancement with mesenteric hematoma (Fig. 9.16). The signs of bowel wall injury include bowel wall thickening (most sensitive but not specific), pneumoperitoneum, bowel wall defect and contrast extravasation. In the presence of bowel perforation, CT findings may include extraluminal air or oral contrast (if administered), or moderate to large volumes of free intraperitoneal fluid without an obvious source such as solid organ injury (Fig. 9.17) [5].

Fig. 9.16

Omental contusion . Contrast-enhanced CT demonstrates fat stranding in omental fat (arrowhead) due to traumatic omental contusion

Fig. 9.17

Small bowel perforation. Contrast-enhanced CT shows extravasation of oral contrast (arrowhead) secondary to small bowel perforation caused by trocar during laparoscopic surgery

Shock bowel or diffuse small bowel ischemia (Figs. 9.18 and 9.19) can occur when a patient becomes severely hypotensive following hemorrhage. Shock develops from decreased circulating blood volume, which is often complicated by derangement of circulatory control and release of vasoconstrictors such as angiotensin II, adrenaline, and noradrenaline. The blood supply to the intestinal mucosa is drastically reduced during marked sympathetic stimulation and is diverted to other crucial organs such as the brain and heart. The resulting splanchnic vasoconstriction leads to intestinal hypoperfusion and, in advanced cases, intestinal ischemia. Mesenteric arterial vasoconstriction and venous constriction of the bowel wall develop after release of angiotensin II, adrenaline, and noradrenaline. The resultant decrease in both arterial perfusion and venous outflow contributes to the enhancement of the bowel mucosa in shock bowel [31]. Bowel hypoperfusion most profoundly affects the intestinal mucosa, which can lead to “third space” fluid loss into the gastrointestinal tract. CT characteristics of shock bowel are diffuse thickening of the small bowel wall (7–15 mm), fluid-filled dilated small bowel, increased contrast enhancement of the small bowel wall, and flattened vena cava. The large bowel will often appear normal in the setting of small bowel ischemia. Table 9.12 summarizes CT findings of bowel and mesenteric injury.

Fig. 9.18

Shock bowel syndrome . (a and b) Contrast-enhanced CT shows hyperenhancing small bowel walls (arrowheads) in a patient with hypovolemia after motor vehicle accident. (c) Contrast-enhanced CT shows hyperenhancing adrenal gland (straight arrow), flattened IVC (arrowhead), and peripancreatic fluid (curved arrow)

Fig. 9.19

Shock bowel syndrome. (a and b) Contrast-enhanced CT shows hyperenhancing small bowel walls and ascites. The IVC (arrowhead) is flattened secondary to hypovolemia. (c) Contrast-enhanced CT shows peripancreatic fluid (arrowheads) and flattened IVC

Table 9.12 CT findings of bowel and mesenteric surgery

In addition to the aforementioned effects of the hypoperfusion complex on the bowel and mesentery, shock adrenal glands play a role in the increased sympathetic stimulation and demonstrate symmetric hyperenhancement on CT. Hypoperfusion results in the release of angiotensin II which stimulates the adrenal cortex of the adrenal glands to produce aldosterone and the adrenal medulla to produce adrenaline and noradrenaline.

Teaching Points

• MDCT with IV contrast is not appropriate for hemodynamically unstable patients with blunt abdominal trauma.

• MDCT with IV contrast is the imaging modality of choice for hemodynamically stable patients with blunt abdominal trauma.

• Findings suggestive of mesenteric injury include ACE into the mesentery, focal mesenteric hematoma or infiltration, bowel wall thickening, or abnormal enhancement with mesenteric hematoma.

• RUG is the study of choice for the diagnosis of urethral injury.

• CT cystography or conventional cystography should be performed following abdomen/pelvis CT if bladder injury is suspected.

• Bowel perforation may show extraluminal air or oral contrast, or moderate to large volume of intraperitoneal free fluid without an obvious source.

• Shock bowel appears as diffuse thickening of the small bowel wall (7–15 mm), fluid-filled dilated small bowel, increased contrast enhancement of the small bowel wall, and flattened vena cava.

Questions

• 1. Which of the following is most likely to be associated with peritoneal fluid on FAST?

  • (a) Injury to head of pancreas

  • (b) Ovulation

  • (c) Injury to middle third of rectum

  • (d) Ascending colon injury

Answer: B

• 2. Subcapsular hematoma which covers 40% of splenic surface is categorized as which grade based on AAST organ injury scale?

  • (a) Grade 1

  • (b) Grade 2

  • (c) Grade 3

  • (d) Grade 4

Answer: B

• 3. Based on AAST organ injury scale, what is the grade of renal injury depicted on the CT (Fig. 9.20 (a) portal venous phase, (b) delayed phase)?

  • (a) Grade 1

  • (b) Grade 2

  • (c) Grade 3

  • (d) Grade 4

Fig. 9.20

Answer: C

• 4. Based on Goldman’s classification for urethral injuries, the urethral injury depicted on the retrograde urethrogram (Fig. 9.21) can be classified as which of the following?

  • (a) Grade III

  • (b) Grade IV

  • (c) Grade IV A

  • (d) Grade V

Fig. 9.21

Answer: D

• 5. The area of increased density on arterial phase imaging (Fig. 9.22 (a) arterial, and (b) portal venous) in the spleen most likely represents which of the following?

  • (a) Pseudoaneurysm

  • (b) Active extravasation of contrast

  • (c) Hematoma

  • (d) Calcification

Fig. 9.22

Answer: A

• 6. What is the pathology depicted on the CT cystogram (Fig. 9.23) in a patient involved in a motor vehicle collision?

  • (a) Extraperitoneal bladder rupture

  • (b) Arterial contrast extravasation

  • (c) Intraperitoneal bladder rupture

  • (d) Ureterocele

Fig. 9.23

Answer: C

• 7. A hepatic intraparenchymal hematoma measuring 12 cm in width is categorized as which grade of injury according to the AAST organ injury scale (Fig. 9.24)?

  • (a) Grade I

  • (b) Grade II

  • (c) Grade III

  • (d) Grade IV

Fig. 9.24

Answer: C

• 8. In the acute trauma setting, the appearance of small bowel wall depicted on the CECT (Fig. 9.25) is seen with which of the following?

  • (a) Enteritis

  • (b) Inflammatory bowel disease

  • (c) Bowel perforation

  • (d) Shock bowel syndrome

Fig. 9.25

Answer: D.